A much-touted vaccine given to teens and preteens to prevent cancers caused by a sexually transmitted virus did not cause or contribute to the death of a 12-year-old Waukesha girl whose mother found her unresponsive in their home on July 30, the Waukesha County medical examiner said Wednesday.

Diphenhydramine intoxication — ingestion of a lethal level of an antihistamine — caused the death of Meredith Prohaska, though the manner of death is undetermined, Medical Examiner Lynda Biedrzycki said in a prepared statement.

"There is no evidence that any vaccination caused or contributed to her death," Biedrzycki said.

Diphenhydramine is a type of antihistamine found in various allergy and sleep medicines, including Benadryl, Tylenol PM, Nytol and Sominex, according to the National Institutes of Health. Overdose occurs when someone accidentally or intentionally takes more than the normal or recommended amount of a drug or medication.

No further details from the 12-year-old's autopsy were provided. If her death had been caused by an interaction with another substance, it would have been noted in the statement about manner of death.

The girl's mother, Rebecca Prohaska, told the news media in early August that she believed her daughter may have had an allergic reaction to the human papillomavirus vaccine, also known as HPV, about six hours after the vaccine was administered in a doctor's office.

The mother's speculation was reported by several television stations and the Journal Sentinel, and was picked up by opponents of childhood vaccinations across the country as inaccurate evidence that the vaccine can kill.

The HPV vaccine, given in three doses starting at age 11 or 12, is the only vaccine currently available to prevent any type of cancer. HPV vaccination is recommended by the Centers for Disease Control and Prevention, the American Academy of Family Physicians, the American Academy of Pediatrics, and the Society for Adolescent Health and Medicine.

The HPV vaccine offers protection from most of the cancers caused by human papillomavirus, known as HPV — a common virus that spreads when an infected person has sexual contact with another person. The nature of how the virus spreads — through sexual contact — has prompted some parents to object to giving the vaccine to preteens.

Some preteens and teens may faint after getting the HPV vaccine, which is why physicians ask them to sit or lie down when they get a shot, and stay like that for about 15 minutes to help prevent fainting and any injury.

Serious side effects from the HPV vaccine are rare, according to the CDC.

Meredith Prohaska was given the HPV vaccine around 10:30 a.m. on July 30, and was dead within six hours.

Rebecca Prohaska told police she had come home from an errand about 4:15 p.m. and found Meredith unresponsive and lying facedown on the living room floor. The child's mother began performing cardiopulmonary resuscitation.

Meredith had vomited. Her lips were purple. She was not breathing and did not have a pulse. Her 6-year-old sister, Margaret, was lying beside her trying to cuddle, according to her mother.

About Karen Herzog

Karen Herzog covers higher education. She also has covered public health and was part of a national award-winning team that took on Milwaukee's infant mortality crisis.